Our long term goal is to gain a molecular understanding of morphogenetic processes in higher organisms by examining a number of events which take place in the development of the limb. In order to meet this goal we will continue to analyze an unique collection of mutations which affect some aspect of limb morphogenesis in the avian embryo. Conceptually we follow the partition of the developmental events into a morphogenetic phase and a phase of cytodifferentiation as first proposed by Zwilling. For studies on the morphogenetic phase we will analyze the events by which the lateral plate mesoderm acquires limb properties through an interaction with somite mesoderm. We will concentrate on chondrogenesis as a measure of cytodifferentiation and we will analyze this developmental event in terms of the coordinate expression of three cartilage specific macromolecules, proteochondroitin sulfate, collagen and a proteochondroitin surfate glyco-protein linker molecule. These three macromolecules will be analyzed as individual entities. They will be further analyzed as they interact with each other (e.g. proteochondroitin sulfate with collagen and proteochondroitin sulfate with glyco-protein linker) in the formation of extracellular matrix.